For example, a monolithic ceramic capacitor, which is one of representatives of monolithic ceramic electronic components, has a structure including a monolithic ceramic element, in which a plurality of inner electrodes are stacked with ceramic layers therebetween, and outer electrodes disposed on the surface of the monolithic ceramic element in such a way as to be connected to the inner electrodes.
Then, as for the outer electrode of such a monolithic ceramic electronic component, for example, an outer electrode having a two-layer structure composed of a first layer in contact with the surface of a bare chip formed from a ceramic sintered body and a second layer disposed on this first layer by stacking has been proposed, wherein the first layer is formed by using an electrically conductive paste prepared by dispersing a metal resinate in an organic binder and an organic solvent and the second layer is formed by using an electrically conductive paste prepared by dispersing a metal powder in a thermosetting resin and an organic solvent (refer to Patent Document 1).
Also, as for another outer electrode, an outer electrode, which is in contact with the surface of a bare chip formed from a ceramic sintered body and which is formed by using an electrically conductive paste prepared by dispersing a metal resinate in an organic binder and an organic solvent, has been proposed (refer to Patent Document 2).
In this regard, it is mentioned that these outer electrodes exhibit good plating liquid resistance in formation of a plating layer and electronic components including these outer electrodes can realize excellent electrical characteristics, reliability, and mechanical characteristics.
However, in general, the electrically conductive paste containing the metal resinate is expensive and there are problems that, for example, an increase in product cost is caused.
On the other hand, in contrast to these electrically conductive pastes containing the metal resinate, for example, an outer electrode formed by using a metal powder serving as an electrically conductive component, glass frit, and an organic vehicle has also been made available to monolithic ceramic electronic components, e.g., a monolithic ceramic capacitor, widely.
Meanwhile, for example, as shown in FIG. 3, a surface mount monolithic ceramic capacitor 130 has a structure in which outer electrodes 135a and 135b are disposed on both end surfaces 134a and 134b of a sintered monolithic ceramic element 133 (ceramic capacitor element) in such a way as to be connected to inner electrodes 131a and 131b, in general, where in the monolithic ceramic element, a plurality of inner electrodes 131a and 131b are stacked with ceramic layers 132 therebetween.
Then, the outer electrodes 135a and 135b are disposed in such a way as to go around from the both end surfaces 134a and 134b of the monolithic ceramic element 133 to side surfaces 136 of the monolithic ceramic element 133. In this regard, the rectangular parallelepiped ceramic element 133 has four side surfaces and the outer electrodes 135a and 135b go around from both end surfaces 134a and 134b, respectively, to the four side surfaces.
In many cases, Ni plating films are formed on the outer electrodes 135a and 135b to prevent solder leaching (dissolution of an outer electrode into solder), or a Sn plating film is further formed on the Ni plating film to ensure the solderability.
However, in a step to form plating films on the outer electrodes 135a and 135b (plating step), a plating liquid penetrates from the front end portions of the going-around portions (going-around front end portion) 144a and 144b of the outer electrodes 135a and 135b into between the monolithic ceramic element 133 and the outer electrodes 135a and 135b, and ceramic components are eluted. As a result, there is a problem that the reliability is degraded because the strength of the monolithic ceramic element 133 in the vicinity of the going-around front end portions 144a and 144b of the outer electrodes 135a and 135b is reduced, a crack occurs during reflow, and bending strength becomes insufficient.
Patent Document 1: Japanese Unexamined Patent Application Publication No. 9-190950
Patent Document 2: Japanese Unexamined Patent Application Publication No. 9-266129